The present invention relates to a magnet wire excellent in windability, lubricity, and abrasion resistance, which keeps its insulating film undamaged when wound into a coil, thereby contributing to improved productivity and yield of coil making.
Electrical equipment has been recently made compact and improved in performance and, in addition, at reduced cost. Along with these tendencies, the fabrication process has been systemized and simplified, and material cost has been reduced.
In the fabrication process of coils for motors, transformers, and the like, all of which play important roles in electrical equipment, an improvement in productivity by a high-speed coil winding process and an improvement in motor performance by an increase in occupation ratio of a magnet wire in a stator slot in a motor cause extensive studies in the advancement of compact arrangements. The systemization and simplification of the process for fabricating coils for motors, transformers, and the like as well as the compact configuration of electrical equipment impose severe conditions on magnet wire coatings used therein. For example, in the coil winding process, magnet wires tend to be brought into contact with pulleys, guides or the like in high-speed coil winding by an automatic winder. In addition, wire tension during the winding process is increased. The insulating coating tends to be damaged, thus causing defects such as a rare short.
Contact forces between magnet wires, between the magnet wire and a core, and between the magnet wire and an inserter blade are increased by an increase in occupation ratio in the stator slot of the motor and by introduction of an automatic inserter. The increases in contact forces mainly cause occurrence of defects. In order to prevent damage to the insulating film during the conventional coil winding process, an oil, paraffin wax or the like is coated on the insulating film to reduce a coefficient of friction thereof. However, such a conventional method cannot solve the above disadvantages.
U.S. Pat. No. 3,413,148 proposes a technique wherein a thin polyethylene layer is formed on a surface of an insulating film. This technique is effected to reduce the coefficient of friction to some extent, but is not expected to greatly improve the abrasion resistance of the insulating film. U.S. Pat. Nos. 3,775,175, 4,390,590 and 4,378,407, British Pat. No. 2,103,868, and Japanese Pat. No. 968283 propose techniques wherein a lubricant is added to or reacts with an insulating enamel to reduce a coefficient of friction so as to improve lubricity of the insulating film itself. These techniques have effects to some extent, but do not essentially prevent damage to the insulating film.
In order to overcome the disadvantages of the conventional techniques, the coefficient of friction must be greatly reduced, and abrasion resistance must be greatly improved.